CBS News has learned that presumptive Republican presidential nominee Mitt Romney is set to meet with casino magnate Sheldon Adelson today at Adelson's offices at the Venetian Hotel in Las Vegas, according to two sources close to Adelson with knowledge of the meeting.

While Adelson's largesse and that of his wife was originally limited to his support for former House Speaker Newt Gingrich, he has indicated his willingness to support the ultimate GOP candidate who runs against President Obama.

So far, it is not known if the billionaire has given to the super PAC supporting Mitt Romney called Restore Our Future.

Adelson and his wife are to date the largest donors to the presidential race, providing $20 million to the super PAC supporting Newt Gingrich called Winning Our Future. In addition, Adelson and his wife branched out in February -- giving a combined $5 million to the GOP Congressional Leadership Fund led by former Sen. Norm Coleman.

Last month, the Romney super PAC Restore Our Future had its weakest fundraising haul with just $4.6 million. That was its lowest monthly fundraising total this year.

The next round of super PAC disclosures will be released on June 20th.